1. Technical Field
The present invention relates to windows for building structures and to methods and apparatus for fabricating such windows.
2. Discussion of the Prior Art
Windows having wooden frames and sashes are the most commercially popular type of window structure but are known to suffer badly from exposure to the elements. Wooden frames may be clad or coated with weather-proofing material; however, this adds considerable cost to an already expensive product. Metal frames and sashes have also been used for windows and are more resistant to deterioration from exposure to the elements. However, metal is a good conductor of thermal energy and must be used in conjunction with thermal breaks to insulate against thermal conduction between the exterior and the interior of the building via the window frame and sashes. The thermal break complicates fabrication of the windows and adds considerably to the overall expense.
Plastic window frames and sashes have been attempted in the prior art, as exemplified by the disclosure in U.S. Pat. No. 4,328,644 (Scott et al). The frames and sashes are constructed from individually-extruded top, bottom and side sections which are cut to the desired length and then secured together by means of screws, welding, etc., at the frame and sash corners. The assembly cost for such windows is quite large, particularly in view of the possibility that individual sections may not be properly cut or processed. In addition, the corner joints of the extruded sections are subject to racking and penetration by air and water.